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/* Copyright (C) 1991, 1992, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <limits.h>
#include <fcntl.h>
#include <utmp.h>
/* Return the login name of the user, or NULL if it can't be determined.
The returned pointer, if not NULL, is good only until the next call. */
char *
getlogin (void)
{
char tty_pathname[2 + 2 * NAME_MAX];
char *real_tty_path = tty_pathname;
char *result = NULL;
struct utmp_data utmp_data = { ut_fd: -1 };
static char name[UT_NAMESIZE + 1];
struct utmp *ut, line;
/* Get name of tty connected to fd 0. Return NULL if not a tty or
if fd 0 isn't open. Note that a lot of documentation says that
getlogin() is based on the controlling terminal---what they
really mean is "the terminal connected to standard input". The
getlogin() implementation of DEC Unix, SunOS, Solaris, HP-UX all
return NULL if fd 0 has been closed, so this is the compatible
thing to do. Note that ttyname(open("/dev/tty")) on those
systems returns /dev/tty, so that is not a possible solution for
getlogin(). */
if (__ttyname_r (0, real_tty_path, sizeof (tty_pathname)) < 0)
return NULL;
real_tty_path += 5; /* Remove "/dev/". */
__setutent_r (&utmp_data);
strncpy (line.ut_line, real_tty_path, sizeof line.ut_line);
if (__getutline_r (&line, &ut, &utmp_data) < 0)
{
if (errno == ESRCH)
/* The caller expects ENOENT if nothing is found. */
errno = ENOENT;
result = NULL;
}
else
{
strncpy (name, ut->ut_user, UT_NAMESIZE);
name[UT_NAMESIZE] = '\0';
result = name;
}
__endutent_r (&utmp_data);
return result;
}
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